Troubleshooting false alarm

Hi, maybe someonebhas encountered this.
Fire alarm goes off due to flalse alarm. Over 150 times in the passed few weeks. Always the same zone, cold area usually below zero so non addrssable set temp heat detectors. All devices have been replaced, all wiring has been chacked and toned multiple times. At the imm module it goes the the non addressable supervisory A/B signal. Im starting to think its the IMM module is somehow shorting that zone. Has anyone encountered this before? Panel and entire system was replaced October 2022. All new wiring etc. I am a master Electrician in Canada and a certified fire alarm installer, but not an expert in FA systems, so i do understand electricity and the way a system works. FA is in northern canada 5 hours travel one direction from nearest town that i live in. So, we replac3d all devices 2 days ago and no alarm until 1am this morning. Help, anyone?

Can you move the devices to another zone to eliminate the possibility of it being circuit related? Also, pull the wires off the panel and check resistance to earth ground. There should be none.

Devices were all replaced, i would think we’d see a trouble alarm of it was going to ground. It can be checked, we still have a guy on site. The zone is bracnched off the main loop, as the main loop is addressable so it has a midule inline to make the faulty zone non addressable, as it is below -40 in the winter in that portion of the building. We have a guy driving up with new module and i told them to replace EOL just in case. No trouble alarms at all, it just randomly goes into fire alarm.

This seems like the wiring in the non-addressable portion is somehow getting shorted - perhaps the insulation between the wires is deteriorating? There could also be an issue with pests chewing on the wires (you may want to call an exterminator).

Thank you, but the cables were all new in October amd are all in armour or conduitm We swapped the pull stn, EOL resistor and the imm module, so far its not gone into alarm again. So one of those 3 items was faulty. What a giant and expensive pain in the behind…